Surface treating aluminum articles



Patented Apr. 30, 1929.

UNITED STATES ALADAR PACZ, 01 EAST CLEVELAND, OHIO.

SURFACE TREATING ALUMINUM ARTICLES.

No Drawing.

This invention relates to the coating of aluminum articles for the purpose of enhancing their artistic appearance, preventing corrosion, or constituting a base for paint, varnish, enamel, lacquer, Japan or other coating. By aluminum I mean not only the pure metal but alloys in which aluminum is preponderant. It has long been a matter of known difiieulty to coat or color articles of aluminum and the object of my present invention is the provision of a particularly cheap, simple, rapid, and reliable process and composition of matter for this purpose.

In my Patent No. 1,551,613 I described methods of coating aluminum articles by immersion in solutions containing ammonia with or without metallic salts designed to change the depth, hardness, or color of the coating so produced. This involved for its successful performance the use of very strong solutions of ammonia heated to a rather high temperature and hence extremely oifensive to workmen and expensive to maintain. In the Roux Patent No. 1,095,-

357, (which I control) there is set forth a process of coating aluminum by the use of an electric potential and an ammoniacal solution but electro-plating is usually run as an independent business and is seldom entrusted to casual factory employees, whereas I have sought a process of such simplicity as to be performed Without skilled attendants. I have discovered that articles of aluminum and itsalloys can be successfully coated and colored without ammonia and fluoride salts.

Without the use of electric current by the use of dipping solutions of certain double The color and nature of the coating can be modified by the addition of salts of various other metals.

Immersion of a pure aluminum article in a solution of a soluble silico fluoride (such Application filed April 16, 1926. Serial No. 102,560.

the nature and amount of such other metal.

In the case of copper aluminum alloys the color thus produced is yellowish, golden or reddish and-in the case of silic'on'alloys grey to black, dependent upon the proportion of the respective constituents and to some extent on the strength of the solution and time of the immersion. The latter conditions, namely time and concentration, are operative only up to a maximum degree dependent upon the alloy composition after which further treatment has no additional effect.

The strengthof the solution which I prefer to employ is one containing from about to about 2% more or less of sodium silico fluoride or other soluble double fluoride having such a dissolving action e. g. sodium zirconium fluoride, sodium titanium fluoride, potassium zirconium fluoride, potassium silico fluoride, potassium titanium fluoride, etc. All the alkali bases can be used and many second metals; the reason I advocate sodium silico fluoride ,is'that it is essentially a waste product and hence cheap and abundant.

The nature of the act-ion may be modified by the production on the etched surface of the aluminum of an added coating containing some other metal in adherent form, and this can be accomplished at the same time and in the same solution and without electrical potential. I have had successful results with additions of silver, nickel, cobalt, zinc, cadmium, antimony, tin, lead, iron, and manganese. These apparently can be added in substantially any soluble form. ()ne of the simplest isthe oxide, and this form although less easily soluble in some cases, is advantageous in maintaining the purity of the bath. Another convenient compound is etc. give entirely successful results. In general the color of the coating produced is a grey of lighter or darker shade and this the carbonate, but the sulphates, chlorides,

coating is of such hardness and adherence as even to stand moderate scratoh brushing. Darker colors can be obtained by using combinations of metals; for example, the use of zinc and antimony in combination gives black colored coating on pure aluminum; likewise zinc and iron. The addition of a small amount of copper to the other metals employed also darkens the coating substantially. The use of soluble manganese salts such as potassium permanganate also has adarkening effect.

I prefer to use a relatively small amount of the metal compound as compared with the double fluoride salt. I have had excellent results with an amount of the metal compound equivalent to onetenth of the amount of fluoride salt present, although I do not restrict myself to these proportions since the same can be modified very substantially in both directions, only it seems to be necessary at least for the best results, that the amount of the metal compound be substantially less than that of the double fluoride.

The solution, whatever its composition within the limits I have described, is preferably used hot and the articles are im merscd therein for periods as low as onehalf minute but usually about one to five minutes. No danger from over treatment need be apprehended, (excepting in the case of pickling the pure aluminum in pure double fluoride) since the effect of an alloyed metal in the article or an added metal in establishments.

Having thus described my invention what I claim is:

1. A dipping solution for producing a colored coating on articles composed at least in part of aluminum which contains a soluble fluorine compound and a salt of one of the metals, silver, nickel, tin, cobalt, zinc, cadmium, iron, manganese, lead, antimony, copper.

2. A dipping solution for producing a black adherent, protective coating on articles made at least in part of aluminum which contains a soluble double fluoride, a soluble zinc salt, and a soluble salt of another nonalkali metal.

3. A dipping solution for aluminum articlescontaining an alkaline silico fluoride and a soluble salt of one of the metals, nickel, cobalt, iron, silver, zinc, cadmium, copper, lead, antimony, manganese, tin.

In testimony whereof I hereunto afiix my signature.

7 v ALADAR PACZ. 

